The seven-day week is used by the majority of the world and is the international standard as specified in ISO 8601.

Origins[link]

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The origin of the seven-day week is the religious significance that was placed on the seventh day by ancient cultures, including the Babylonian and Jewish civilizations. Jews celebrated every seventh day, within a continuous cycle of seven-day weeks, as a holy day of rest from their work, although it is possible that the Hebrew origin of the seven-day week was lunar, and not perpetual. Similarly, the Babylonians celebrated the seventh day of each seven-day week as a holy day, but adjusted the number of days of the final week in their month so that their monthly calendar would always commence on the new moon. This may further be reflected in the contemporary and traditional Zoroastrian calendars that relates to the first, seventh and so on days of the month as pertaining to Ahura Mazda (God).^{[citation needed]} Historically, a number of other cultural groups, such as Christians and Muslims, have continued to regularly hold religious events on a specific day within each seven-day week.

The seven-day week is approximately a quarter of a lunation, so it has been proposed that this is the implicit, astronomical origin of the seven-day week. However, there are a number of problems with the proposal. The seven-day week is actually only 23.7% of a lunation, which means that a continuous cycle of seven-day weeks rapidly loses synchronisation with the lunation. The problem is compounded by the fact that a lunation is only the mean time for the lunar phase cycle, with each individual lunar phase varying in length. Also, the duodecimal (base-12) and sexagesimal (base-60) numeral systems have historically been the primary systems used to divide other chronological and calendar units. Therefore, it is not immediately apparent why the seven-day week was selected by ancient cultures, rather than a week that included a number of days that was a factor of these numeral systems, such as a six-day or a twelve-day week, or a week that divided the lunation more accurately using a factor of these number systems, such as a five-day or ten-day week.^{[original research?]} There are no historical Jewish or Babylonian records that confirm that these cultures explicitly defined the seven-day week as a quarter of a lunation.

Ancient Near East[link]

The Babylonian Imago Mundi, dated to the 6th century BC (Neo-Babylonian Empire).^[1] The map shows Babylon on the Euphrates, surrounded by a circular landmass showing Assyria, Armenia and several cities, in turn surrounded by a "bitter river" (Oceanus), with seven islands arranged around it so as to form a seven-pointed star.

Counting from the new moon, the Babylonians celebrated the 7th, 14th, 21st, and 28th as "holy-days", also called "evil days" (meaning "unsuitable" for prohibited activities). On these days officials were prohibited from various activities and common men were forbidden to "make a wish", and at least the 28th was known as a "rest-day".^{[citation needed]} On each of them, offerings were made to a different god and goddess. Tablets from the 6th-century BC reigns of Cyrus the Great and Cambyses indicate these dates were sometimes approximate. The lunation of 29 or 30 days basically contained three seven-day weeks, and a final week of eight or nine days inclusive, breaking the continuous seven-day cycle. The Babylonians additionally celebrated the 19th as a special "evil day", the "day of anger", because it was roughly the 49th day of the (preceding) month, completing a "week of weeks", with sacrifices and prohibitions.^{[citation needed]} Reconstruction of a broken tablet seems to define the rarely attested Sapattu^m or Sabattu^m as the 15th day of the lunation: this word is cognate with Hebrew Shabbat, but is monthly rather than weekly. It is regarded as a form of Sumerian sa-bat ("mid-rest"), attested in Akkadian as um nuh libbi ("day of mid-repose").^[2]

The seven-day week appears in the Creation story in the Book of Genesis, in the Hebrew Bible, where Elohim (God) is said to have created the heavens and the earth in six days and rested on the seventh (Genesis 1:1-2:3). In the Book of Exodus, the fourth of the ten commandments is to rest on the seventh day, the Sabbath, which can be seen as implicating a seven-day week social institution (Exodus 20:8-11).

Classical Antiquity[link]

Frank C. Senn in his book Christian Liturgy: Catholic and Evangelical points to data suggesting evidence of an early continuous use of a seven-day week; referring to the Jews during the Babylonian Captivity in the 6th century BCE,^[3] after the destruction of the Temple of Solomon. The ancient Romans traditionally used the eight-day nundinal cycle, but after the adoption of the Julian calendar, in the time of Augustus, the seven-day week came into use. For a while, the week and the nundinal cycle coexisted, but by the time the week was officially adopted by Constantine in AD 321^[4] the nundinal cycle had fallen out of use. The association of the days of the week with the Sun, the Moon, and the five planets visible to the naked eye dates to the Roman era (2nd century).

Christian Europe[link]

The seven-day weekly cycle is reputed^{[citation needed]} to have remained unbroken in Europe for almost two millennia, despite changes to the Alexandrian, Julian, and Gregorian calendars. The date of Easter Sunday can be traced back through numerous computistic tables to an Ethiopic copy of an early Alexandrian table beginning with the Easter of 311 AD.^[5]

Adoption after other systems[link]

China[link]

The earliest known reference in Chinese writings to a seven-day week is attributed to Fan Ning, who lived in the late 4th century in the Jin Dynasty, while diffusions from the Manichaeans are documented with the writings of the Chinese Buddhist monk Yi Jing and the Ceylonese or Central Asian Buddhist monk Bu Kong of the 7th century (Tang Dynasty).

Japan[link]

The Chinese transliteration of the planetary system was soon brought to Japan by the Japanese monk Kobo Daishi. Surviving diaries of the Japanese statesman Fujiwara Michinaga show the seven-day system in use in Heian Japan as early as 1007. In Japan, the seven-day system was kept in use for astrological purposes until its promotion to a full-fledged Western-style calendrical basis during the Meiji era.

Hindu[link]

The seven-day week may have been in use during the Vedic Period, although according to Pandurang Vaman Kane, author of History of Dharmasastra, "this is not conclusive".

The Pañcasiddhāntikā mentions 'Monday'. The Garga dated 1st Century BCE, refers to the seven-day week, Sunday to Saturday.

He concludes "the above references furnish a terminus ad quem (viz. 1st century BCE–1st century CE) The terminus a quo cannot be stated with certainty".^[6][7]

France[link]

France discontinued the seven-day week for a ten-day week with the introduction of the republican calendar in 1793. The Concordat of 1801, which re-established the Roman Catholic Church in France, also restored the seven-day week, beginning with Easter Sunday, 18 April 1802.

Soviet Union[link]

In 1929, the USSR discontinued the seven-day week for a five-day week, then a six-day week. While the days were still named according to the seven-day week, the work schedules were rotated in five- and six-day periods. The seven-day week was reintroduced on 27 June 1940.

Week numbering[link]

Weeks in a Gregorian calendar year can be numbered for each year. This style of numbering is commonly used (for example, by schools and businesses) in some European and Asian countries, but rare elsewhere.

ISO 8601 includes the ISO week date system, a numbering system for weeks – each week begins on a Monday and is associated with the year that contains that week's Thursday (so that if a year starts in a long weekend Friday–Sunday, week number one of the year will start after that). For example, week 1 of 2004 (2004W01) ran from Monday 29 December 2003 to Sunday, 4 January 2004, because its Thursday was 1 January 2004, whereas week 1 of 2005 (2005W01) ran from Monday 3 January 2005 to Sunday 9 January 2005, because its Thursday was 6 January 2005 and so the first Thursday of 2005. The highest week number in a year is either 52 or 53 (it was 53 in the year 2004). Schematically, this ISO convention translates as follows:

In some countries, though, the numbering system is different from the ISO standard. At least six numberings are in use:^[8][9]

Facts and figures[link]

• 1 week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds (except at daylight saving time transitions or leap seconds)
• 1 Gregorian calendar year = 52 weeks + 1 day (2 days in a leap year)
• 1 week = 1600⁄6957 ≈ 22.9984% of an average Gregorian month

In a Gregorian mean year there are 365.2425 days, and thus exactly 52 71⁄400 or 52.1775 weeks (unlike the Julian year of 365.25 days or 52 5⁄28 ≈ 52.1786 weeks, which cannot be represented by a finite decimal expansion). There are exactly 20871 weeks in 400 Gregorian years, so 30 April 1611 was a Saturday just like 30 April 2011.

A system of Dominical letters has been used to determine the day of week in the Gregorian or the Julian calendar.

See also[link]

• Calculating the day of the week
• Dominical letter
• Workweek
• Hebrew calendar
• Broadcast calendar
• Lunar phase

References[link]

External links[link]

• Week Wheel for Children

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Austin Roberts

Austin Roberts (3 January 1883 – 5 May 1948) was a South African zoologist. He is best known for his Birds of South Africa, first published in 1940. He also studied the mammalian fauna of the region: his work The mammals of South Africa was published posthumously in 1951. The 7th edition of Roberts' Birds of Southern Africa which appeared in 2005, is the standard work on the region's birds.

Life[link]

Roberts, son of a church minister, was born in Pretoria and grew up in Potchefstroom, South Africa. He gained much of his early knowledge of zoology from Thomas Ayres (1828–1913), one of South Africa's first amateur ornithologists. Roberts was employed by the Transvaal Museum from 1910 to 1946. From this base he studied the birds and mammals of South Africa. To further research, he established a collection of ca. 30,000 bird and 13,000 mammal specimens at the museum. He was author of several manuscripts and articles in scientific publications. In 1935 the University of Pretoria awarded him an honorary doctorate degree. Austin Roberts died on 5 May 1948 in a motor car accident in the Transkei region.

The Austin Roberts Bird Sanctuary in Pretoria is named in his honour.

Works[link]

• The Mammals of South Africa. Johannesburg 1951–54 (p. m.)
• Our South African Birds (Ons Suid-Afrikaanse voëls). Cape Times, Cape Town 1941.
• The Birds of South Africa. H.F.&G.Witherby Ltd., London, 1940.
• Museums, higher vertebrate zoology and their relationship to human affairs. Pretoria 1935.

Literature[link]

• Charles Kimberlin Brain: Austin Roberts. Cape Town 1998. ISBN 0-620-22883-0

See also[link]

• Claude-Gibney Finch-Davies

References[link]

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